Lignite Waste Research Articles

Synergistic effects of coal waste derived humic substances and inorganic fertilizer as soil amendments for barley in sandy soil

Increasing pressures on land resources requires increased land use efficiency. Over 900 million ha of sandy soils throughout the world are extensively used for agricultural crop production, most requiring nutrient inputs. Although use of humic substances together with inorganic fertilizer as soil amendments has been introduced, their synergistic effects on plant growth in sandy soils are not well addressed. We assessed the efficacy of a lignite waste derived humic substance on barley (Hordeum vulgare L.) growth, with and without inorganic fertilizer. Ten treatments were applied to sandy soils, comprising sole application of the humic product at four rates (NH1, NH2, NH3, NH4), sole application of fertilizer (F), and their combinations (F + NH1, F + NH2, F + NH3, F + NH4). Synergistic effects of nano humus and fertilizer were more notable than the corresponding sole application, particularly on plant biomass and seed production. Combined application with inorganic fertilizer increased root biomass by 92 % (0.1 g per plant), shoot biomass by 80 % (0.5 g per plant), root length by 24 % (3.6 cm), and seed production by 38 % (5 seeds per head) averagely relative to the untreated control, suggesting a strong synergistic effect. The increased seed production was particularly important from an agricultural perspective. Four application rates of nano humus all showed beneficial effects on barley growth with no significant differences. The most distinct positive effect of the humic product as a sole application was on root growth. Our study confirmed that a lignite waste derived humic product, nano humus, together with fertilizer may be an effective soil amendment to enhance agricultural plant growth in sandy soil regions.

Valorizing lignite waste into engineered nitro-humic fertilizer: Advancing resource efficiency in the era of a circular economy

This study investigates using lignite waste as a carrier matrix for creating engineered nitro-humic fertilizer (NHF). The NHF is synthesized through an innovative ozone oxidation method and nitrogen enrichment. Agronomic efficiency was evaluated through maize growth responses, soil incubation experiments, and fertilizer performance, comparing NHF to commercial urea and NPK fertilizers. Nitrogen release patterns and kinetic models were studied to understand the nitrogen release mechanism of NHF. The engineered structure of NHF displayed globular-like, microporous, and heterogeneous properties, with a negative charge density of 48.85 mV and lower thermal stability of aliphatic carbons. The NHF exhibited a remarkable capability to increase water-holding capacity by up to 48% and extend the water-retention period by 57% during 30 d of soil application. NHF significantly reduced soil urease enzyme activity by more than two-fold. It exhibited a longer nitrogen release period (77 d) with a slow-release pattern, releasing 71.75% of total nitrogen compared to 88.5% in 14 d for urea. The simple Elovich model accurately predicted NHF's nitrogen release kinetics (R2 = 0.9943), identifying Fickian diffusion-based controlled release. Applying NHF improved multiple aspects of maize growth: height, stem diameter, biomass, root weight, leaf area, SPAD value, and leaf nitrogen concentration. Total chlorophyll, carotenoid, and nitrogen uptake also greatly increased compared to the control sample. NHF exhibited superior nitrogen use efficiency (41.5%) and agronomic fertilizer efficiency (36.22%) compared to urea and even surpassed commercial NPK fertilizers. Generally, the produced NHF is an eco-friendly alternative to slow-release fertilizers, offering the advantages of humic substances and nitrogen fertilizers.

Pilot Scale Testing of Lignite Adsorption Capability and the Benefits for the Recovery of Rare Earth Elements from Dilute Leach Solutions

Naturally occurring organic materials containing humic acids show a strong affinity towards rare earth elements (REE) and other critical elements. Leaching experiments on lignite coal waste produced from construction sand production revealed that the contained REEs were associated with the organic matter. Furthermore, adsorption studies revealed that the lignite waste was capable of extracting REEs from a model solution and increased the REE content of the lignite waste by more than 100%. As such, this study aimed to utilize the lignite waste to adsorb REEs from pregnant leach solutions and acid mine drainage sources having low REE concentrations and subsequently leach the lignite material to produce pregnant leach solutions containing relatively high amounts of REEs, which benefits the performance and economic viability of downstream separation and purification processes. An integrated flowsheet was developed based on this concept and tested at a pilot scale. The pregnant leachate solution (PLS) was generated from a heap leach pad containing 2000 tons of Baker seam coarse refuse. The pilot scale circuit was comprised of aluminum precipitation, adsorption using the waste lignite, and rare earth-critical metal (RE-CM) precipitation stages in succession. The results indicated that the aluminum precipitation stage removed over 88% and 99% of the Al and Fe, respectively. The adsorption stage increased the REE content associated with the waste lignite from 457 ppm to 1065 ppm on a whole mass basis. Furthermore, the heavy REE (HREE) content in the feedstock increased by approximately 250%, which raised the percentage of HREE in the REE distribution by 19 absolute percentage points. In addition to the REEs, concentrations of other critical elements such as Mn, Ni, and Zn also improved by 75%, 37%, and 250%, respectively. Bench-scale tests revealed that increasing the solids concentration in the waste lignite and PLS mix from 1% to 20% by weight enhanced the adsorption efficiency from 32.0% to 99.5%, respectively. As such, a new flowsheet was proposed which provides significantly higher REE concentrations in the PLS that can be fed directly to solvent extraction and/or oxalic acid precipitation and, thereby, enhancing process efficiency and economics.

A new strategy for treating Pb2+ and Zn2+ pollution with industrial waste derivatives Humin

Metal pollution caused by industrial waste accumulation is a long-term and far-reaching problem. Humin (HM), as a highly condensed organic component insoluble in alkaline or water solution, is often discarded as humic acid industrial waste. However, the abundant active functional groups in HM reported by some researches make it possible for HM to remove metals. In this study, a waste reuse strategy was proposed to reduce the pressure of industrial metal pollution on the environment. HM was obtained from lignite waste residue. Scanning electron microscopy, energy spectrum and Fourier infrared spectroscopy, combined with the adsorption models were employed to reveal the mechanism of HM adsorption. The results showed that HM had multiple adsorption mechanism and high biological stability. The adsorption capacity of HM to Zn2+ and Pb2+ were 194.88 mg/g and 289.59 mg/g respectively. HM adsorbed Zn2+ mainly by physical multilayer adsorption. And the adsorption of Pb2+ by HM was mainly a monolayer chemical reaction, which depended on its active functional groups and the exchange of valence electrons. Notably, HM could simultaneously remove Pb2+ and Zn2+ and almost did not affect its original adsorption capacity to single ions. These results will provide a new strategy for the treatment of metal pollution in the future and alleviate the pressure of multiple metal pollution of the environment.

Enzymatic Activity of Soil after Applying Mineral Fertilizers and Waste Lignite to Maize Grown for Silage

This paper examines the effect of mineral fertilizers and waste lignite, the latter applied to the preceding crop, on the enzymatic activity of soil. The research was conducted between 2014 and 2016 at the Agricultural Experimental Station of the Siedlce University of Natural Sciences and Humanities in Zawady (Poland). The following treatment combinations were involved: 1—control; 2—NPKMgS; 3—NPKMgS + 20 N; 4—NPKMgS + 40 N; 5—NPKMgS + 60 N. Three varieties of maize grown for silage constituted the second research factor. Mineral fertilizers were applied at the following doses (pre-sowing): N-100, P-35, K-125, Mg-12 and S-14 kg ha−1. Nitrogen was additionally applied as top dressing with 3, 4, and 5 treatment combinations at 20, 40, and 60 kg ha−1. Waste lignite was applied to the preceding crop on two plots (3 and 4), in 1 and 5 t ha−1 doses. In the subsequent years, the significantly highest content of soil organic carbon was recorded on the NPKMgS + 60 N plot (1.12%; 0.98% and 1.16%). With 49.25 and 51.95 mg NH4-N h–1 kg–1 DM, urease activity in the soil treated with NPKMgS + 20 N and NPKMgS + 40 N was 56.95% and 65.55% higher than in the control plot soil. Throughout the experimental years, acid phosphatase activity did not vary much and amounted to 3.51–3.53 mmol PNP h–1 kg–1 DM. Mineral fertilizers significantly increased the activity of alkaline phosphatase and dehydrogenases in relation to the control. To ensure the high enzymatic activity of the soil and a high biochemical index of soil fertility, pre-sowing fertilizers at the level of 100 kg N, 35 kg P, 125 kg K, 12 kg Mg, and 14 kg S per hectare and top dressing of 20 kg N or 40 kg N per hectare are recommended. At the same time, it is advisable to use 1 t ha–1 or 5 t ha–1 of waste lignite of low energy value on the preceding crop.

Meso-porous activated carbon from lignite waste and its application in methylene Blue adsorption and coke plant effluent treatment

Coke plant wastewater contains many toxic pollutants such as phenol, cyanide, and ammonia, etc., handling and disposal of which has a significant impact on the environment and human health. A novel adsorbent based on lignite extraction waste was prepared and its effect on the removal of simulated methylene blue, phenol and colour (ortho, para-benzo quinone) from real coking wastewater was investigated. Lignite waste (residue) after humic acid separation has a significant quantity of oxidized functional groups along with residual KOH, which makes it suitable for the preparation of activated carbon with high surface area. Since hydrothermal extraction breaks coal-mineral-pore aggregate, the separation efficiency of ash-bearing minerals improved, 11 % ash coal prepared from the residue with 81.6 % yield. Prepared activated carbon from low ash residue has a mesoporous surface (49.8 nm pore size), 0.554 cm3/g of total pore volume, and 980 m2/gram BET surface area. The adsorption kinetics followed pseudo-second order (R2 = 0.984) for methylene blue, pseudo-second-order (R2 = 0.978) for phenol, and pseudo-first-order (R2 = 0.935) for colour adsorption. Adsorption isotherm at equilibrium shows a maximum adsorption capacity of 120 mg/g for methylene blue, 20.49 mg/g for phenol and 588.23 PtCo/g for colour. The adsorption isotherm was in good agreement with Langmuir isotherm (R2 = 0.989−0.994) compared to Freundlich model (R2 = 0.924−0.982). The presence of negatively charged surface favours the uptake of cationic groups. Apart from phenol and colour, the adsorbent can remove total organic carbon (TOC) by 93.6 % and thiocyanide by 6.7 %. Adsorbent reutilization studies show that, the regenerated adsorbent by thermal treatment can be used for 3 cycles.

Valorization of lignite wastes into humic acids: Process optimization, energy efficiency and structural features analysis

The present work investigates the optimization of humic acids (HAs) production from lignite processing wastes using a developed mechanical agitated (MA) tank reactor based on the results of response surface methodology (RSM). The structures of the obtained HAs were characterized using elemental analysis, spectroscopy, scanning electron microscopy (SEM), particle size distribution (PSD), acidic functional groups, and ash content. The highest extraction efficiency of HA was 54.2%, which was obtained from the MA tank reactor under optimal conditions of using 0.5 M NaOH, the reaction time of 4 h, stirring speed of 850 rpm, and temperature of 70 °C. The developed MA tank reactor was capable of improving the HA extraction and energy efficiency of the process up to 26.9% and 24.8%, respectively, compared to the conventional magnetic stirred (MS) glass reactor. The extracted HA from the MA tank reactor exerted better quality indices, including higher oxygen content (37.02%), higher C/N and O/C ratios (61.26 and 0.47, respectively), higher total acidity and phenolic-OH contents (8.87 and 5.6 meq.g−1, respectively), higher E4/E6 ratio (3.765), more homogeneously porous structure, higher specific surface area, lower H/C ratio (0.64), and lower ash content (2.2%), than the MS method, which indicate its suitability in agricultural applications.

Extraction and purification of humic acids from lignite wastes using alkaline treatment and membrane ultrafiltration

Abstract The cleaner production of high purity and safe humic acid (HA) with very low concentration of heavy metals leads to achieve a final product with potential economic value in agriculture, biomedicine, environment and so on. This can be obtained by environmental-friendly separation of low molecular weight fulvates and inorganic elements present in humic alkaline solutions. The aim of this study is the alkaline extraction of solutions containing humates and fulvates derived from lignite wastes followed by purification of humates using membrane processes. A polysulfone 5 kDa molecular weight cut-off membrane in a plate and frame module was used for ultrafiltration of lignite coals-derived alkaline extracts. The effects of operating parameters including transmembrane pressure (TMP) at four levels (1, 2, 3, and 4 bar), feed flow rate (FFR) at five levels (5, 15, 25, 35, and 45 ml s−1) and processing temperature at three levels (35, 45, and 55 °C) were investigated on permeate flux of fulvate compounds, membrane fouling, purity percentage and ash contents of the HA product. Results showed that the highest permeate flux, the lowest membrane fouling, and the most desirable qualitative/quantitative properties of the purified HA was obtained at TMP of 3 bar, FFR of 45 ml s−1 and temperature of 45 °C. The results of ICP-OES analysis showed very low concentrations of heavy metals and inorganic elements in the purified HA while the FT-IR results confirmed the ICP-OES findings and revealed the rich carboxylic and phenolic functional groups of the final product.

Nox reduction from biodiesel exhaust by plasma induced ozone injection supported by lignite waste adsorption

This paper explores the technique of ozone injection to induce reactions leading to NO conversion in a diesel engine exhaust and subsequent adsorption by lignite ash, an industrial waste from lignite coal fired power plants. Experimental investigations were carried out using a diesel engine fuelled by biodiesel, prepared from pongamia pinnata, a native Indian plant. Ozone is produced from dry air in a Dielectric Barrier Discharge (DBD) reactor by the application of high voltage. The choice of the high voltage was made after a comparative study between high frequency AC and unipolar repetitive pulse source, with the latter consuming lesser power for given ozone production. By injecting ozone, the higher composition of NO in biodiesel exhaust gets oxidized to higher oxides of nitrogen in general and NO2 in particular. This NO2 can be adsorbed in the lignite fly ash pellets as successfully demonstrated in this paper. This combined ozone injection-lignite ash adsorption technique has resulted in an overall removal efficiency of oxides of nitrogen (NOx) as high as 95% even under loaded conditions. A comparison has also been made between the ozone injection technique and direct plasma treatment of exhaust for NOx removal.

The Upgradation of Lignite Mining Waste Into Marketable Carbonaceous Fuel by the Selective Breakage Technique

The inter clay lignite waste from lignite mining in Giral block of Barmer district of Western Rajasthan has been transformed into marketable high calorific carbonaceous fuel, using a selective breakage technique. The coal can be cleaned near the mine mouth without using water; it will avoid transportation of rocks to a distance and also avoid the water pollution problem associated with the slurry ponds. The dry process will be economical as it will not utilize water and, thus, no dewatering or drying of the product will be required. Experiments were conducted with a coal sample containing 9.07% fixed carbon, 33.43% ash, 22.50% volatile matter, and marginally lower calorific value 1,869 Kcal/kg. The preliminary data indicate that by decreasing the size of coal fraction, the energy contents increasing gradually. The highest result was obtained for the size fraction (−) 2.36 to (+) 1 mm of lignite sample.

The utilization possibility of waste lignite as a raw material in the process of obtaining humic acids preparations

Abstract In the light of environmental law utilization lignite waste in non-energy sectors of the economy is a rational way to manage them. Lignite due to the lower degree of coalification and calorific value as well as a high content of humic substances becomes a valuable component of fertilizer. The paper presents the possibility of using lignite waste as a raw material in the process of obtaining humic acids with 0.1 M NaOH. The idea of the process combines production, environmental and economic purposes. After the extraction process of humic acids and considering the possibility of using waste formed during the process, were carried out a number of studies to assist in choosing the best solution to its management.

Workability and strength of lignite bottom ash geopolymer mortar

In this paper, the waste lignite bottom ash from power station was used as a source material for making geopolymer. Sodium silicate and sodium hydroxide (NaOH) were used as liquid for the mixture and heat curing was used to activate the geopolymerization. The fineness of bottom ash, the liquid alkaline/ash ratio, the sodium silicate/NaOH ratio and the NaOH concentration were studied. The effects of the additions of water, NaOH and napthalene-based superplasticizer on the workability and strength of the geopolymer mortar were also studied. Relatively high strength geopolymer mortars of 24.0–58.0 MPa were obtained with the use of ground bottom ash with 3% retained on sieve no. 325 and mean particle size of 15.7 μm, using liquid alkaline/ash ratios of 0.429–0.709, the sodium silicate/NaOH ratios of 0.67–1.5 and 7.5–12.5 M NaOH. The incorporation of water improved the workability of geopolymer mortar more effectively than the use of napthalene-based superplasticizer with similar slight reduction in strengths. The addition of NaOH solution slightly improves the workability of the mix while maintaining the strength of the geopolymer mortars.

Cleaner co-combustion of lignite–biomass–waste blends by utilising inhibiting compounds of toxic emissions

In this paper, the co-combustion behaviour of coal with wastes and biomass and the related toxic gaseous emissions were investigated. The objective of this work is to add on towards a cleaner co-combustion of lignite-waste-biomass blends by utilizing compounds that could inhibit the formation of toxic pollutants. A series of co-combustion tests was performed in a pilot scale incinerator, and the emissions of polychlorinated dibenzo-p-dioxins (PCDDs) and dibenzofurans (PCDFs) were measured. The co-combustion behaviour of lignite with olive kernels, MDF and sawdust was studied and the ability of additives such as urea, almond shells and municipal sewage sludge to reduce the PCDD/F emissions was examined. All blends were proven good fuels and reproducible combustion conditions were achieved. The addition of inhibitors prior to combustion showed in some cases, relatively high PCDD/F emissions reduction. Among the inhibitors tested, urea seems to achieve a reduction of PCDD/F emissions for all fuel blends, while an unstable behaviour was observed for the others.

06/01756 Low-grade coal and biomass co-combustion on fluidized bed: exergy analysis: Martín, C. et al. Energy, 2006, 31, (2–3), 330–344

In this paper, the co-combustion behaviour of coal with wastes and biomass and the related toxic gaseous emissions were investigated. The objective of this work is to add on towards a cleaner co-combustion of lignite–waste–biomass blends by utilizing compounds that could inhibit the formation of toxic pollutants. A series of co-combustion tests was performed in a pilot scale incinerator, and the emissions of polychlorinated dibenzo-p-dioxins (PCDDs) and dibenzofurans (PCDFs) were measured. The co-combustion behaviour of lignite with olive kernels, MDF and sawdust was studied and the ability of additives such as urea, almond shells and municipal sewage sludge to reduce the PCDD/F emissions was examined. All blends were proven good fuels and reproducible combustion conditions were achieved. The addition of inhibitors prior to combustion showed in some cases, relatively high PCDD/F emissions reduction. Among the inhibitors tested, urea seems to achieve a reduction of PCDD/F emissions for all fuel blends, while an unstable behaviour was observed for the others.

Effects of reclamation measures on plant colonization on lignite waste in the eastern Pyrenees, Spain

Abstract. This paper deals with vegetation establishment on waste dumps in the montane and submontane belts of the eastern Pyrenees, where submediterranean Quercus humilis forests, Pinus sylvestris forests and mesoxerophilous pastures make up most of the landscape; these are considered as target communities for reclamation. The waste consists of marl and lime regolith, very poor in nutrients and structure (Poch et al. 1989). The dumps were terraced in 1985–1986; some were left for spontaneous re‐colonization and others were reclaimed in various ways. In 1992 we took 36 vegetation samples on the dumps, based on the point quadrat procedure, to evaluate the colonization status and the differences between reclamation techniques. The samples were analysed on the basis of their species composition (ecological groups and multivariate analysis) and structural aspects (coverage, diversity, etc.). Reclamation treatment results varied widely, most of the dumps showing a low degree of naturalness. Colonizing vegetation ranged from a mixture of opportunist and stress‐resistant taxa, forming poorly covered surfaces on the dumps where colonization has been poor, to dense grasslands dominated by one (or a few) introduced competitive grass species, where reclamation procedures had been intensive. Sowing treatments, where pasture species were sown onto dumps, produced intermediate results, as resulting vegetation cover was similar to control plots and naturalness was low, but in a few cases they yielded more interesting swards, fairly dense and diverse, and including high numbers of spontaneous species. Choice of sown species and proximity to undisturbed vegetation accelerate succession.

99/03693 Synthesis of zeolite from waste lignite ash from Thailand: Virakornphanich, P. and Egashira, K. Solid Sci. Plant Nutr., 1998, 44, (4), 707–710

99/03693 Synthesis of zeolite from waste lignite ash from Thailand: Virakornphanich, P. and Egashira, K. Solid Sci. Plant Nutr., 1998, 44, (4), 707–710

Synthesis of zeolite from waste lignite ash from Thailand

Almost all the lignite ash from the coal thermal power plants in Maemoa, Lumpang Province, Thailand is disposed of as solid wastes. However, the number of reclaimed sites for the disposal of the wastes is not sufficient to handle the large amount of wastes. Therefore, the development of a technique for the utilization of lignite ash is essential to preserve the environment and to recycle the waste materials. Lignite ash is composed of inorganic compounds mainly present as glasses resulting from fusion during their combustion. The chemical composition of these glasses is similar to that of volcanic glass in nature and changes easily to zeolite-like substances by hydrothermal treatment with an alkali. Henmi (1987) reported the synthesis of hydroxysodalite, a kind of zeolite, from waste coal ash. Zeolites are crystalline, hydrated aluminosilicates with a three-dimensional crystal structure and have the attractive cation-exchange properties in agricultural applications (Ming and Mumpton 1989). In the present study, attempts were made to synthesize zeolitelike substances from lignite ash from Thailand, in order to develop a new method for the disposal of industrial wastes. Although the synthesis of zeolite-like substances from waste coal ash had been reported in different countries after the publication of Henmi (1987), this method was applied for the first time in Thailand for the treatment of lignite ash.

97/02436 Mixed fuel processing plant ‘Schwarze Pumpe’ in Germany for processing waste lignite products. A successful year of operation

97/02436 Mixed fuel processing plant ‘Schwarze Pumpe’ in Germany for processing waste lignite products. A successful year of operation

97/00929 Mixed fuel processing plant ‘Schwarze Pumpe’ in Germany for processing waste lignite products. A successful year of operation

This paper is concerned with the development of a novel process for the production of a gas rich in hydrogen and carbon monoxide by means of pressure gasification of pulverized brown coal. In the future, this process will be mainly utilized for the gasification of low grade coal, i.e. high-ash and salt-containing brown coal. The technology, including test plants already constructed, are described in this paper. The commissioning of a large-scale plant at VEB Gaskombinat Schwarze Pumpe was the first step towards the industrial use of this process, which can also be applied to pulverized hard coal and coke dust.